U.S. patent application number 15/774614 was filed with the patent office on 2018-12-06 for air conditioner.
The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Yusuke ADACHI, Yasuhide HAYAMARU, Komei NAKAJIMA, Yusuke TASHIRO.
Application Number | 20180347875 15/774614 |
Document ID | / |
Family ID | 58796595 |
Filed Date | 2018-12-06 |
United States Patent
Application |
20180347875 |
Kind Code |
A1 |
NAKAJIMA; Komei ; et
al. |
December 6, 2018 |
AIR CONDITIONER
Abstract
An air conditioner includes a compressor, a condenser, an
expansion valve, an evaporator, and a temperature detection unit.
The temperature detection unit is attached to the condenser and is
configured to detect a temperature of the refrigerant in the
condenser. The expansion valve is configured to be capable of
adjusting a flow rate per unit time of the refrigerant flowing
through the expansion valve by adjusting a degree of opening of the
expansion valve. The degree of opening of the expansion valve is
increased when the temperature of the refrigerant detected by the
temperature detection unit rises, and the degree of opening of the
expansion valve is decreased when the temperature of the
refrigerant detected by the temperature detection unit falls.
Inventors: |
NAKAJIMA; Komei; (Tokyo,
JP) ; TASHIRO; Yusuke; (Tokyo, JP) ; HAYAMARU;
Yasuhide; (Tokyo, JP) ; ADACHI; Yusuke;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
58796595 |
Appl. No.: |
15/774614 |
Filed: |
December 2, 2015 |
PCT Filed: |
December 2, 2015 |
PCT NO: |
PCT/JP2015/083917 |
371 Date: |
May 9, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 49/02 20130101;
F25B 2341/062 20130101; F25B 2600/2513 20130101; F25B 2700/21162
20130101; F25B 2341/0662 20130101; F25B 2341/063 20130101; F25B
41/067 20130101; F25B 41/062 20130101 |
International
Class: |
F25B 41/06 20060101
F25B041/06 |
Claims
1. An air conditioner comprising: a compressor configured to
compress refrigerant, a rotation number of the compressor being
variably controllable; a condenser configured to condense the
refrigerant compressed by the compressor; an expansion valve
configured to decompress the refrigerant condensed by the
condenser; an evaporator configured to evaporate the refrigerant
decompressed by the expansion valve; and a temperature detection
unit configured to detect a temperature of the refrigerant, the
expansion valve being configured to be capable of adjusting a flow
rate per unit time of the refrigerant flowing through the expansion
valve by adjusting a degree of opening of the expansion valve, the
expansion valve being a temperature-type expansion valve, the
temperature detection unit being a temperature sensitive cylinder,
and the temperature sensitive cylinder being housed in an outdoor
unit, the degree of opening of the expansion valve being increased
when the temperature of the refrigerant detected by the temperature
detection unit rises, and the degree of opening of the expansion
valve being decreased when the temperature of the refrigerant
detected by the temperature detection unit falls.
2-3. (canceled)
4. The air conditioner according to claim 1, wherein a flow rate
coefficient of the expansion valve is increased when the
temperature of the refrigerant detected by the temperature
detection unit rises, and the flow rate coefficient of the
expansion valve is decreased when the temperature of the
refrigerant detected by the temperature detection unit falls.
5. The air conditioner according to claim 1, wherein the expansion
valve includes a first flow path, and a second flow path having a
flow rate lower than that of the first flow path, and the expansion
valve is switched to the first flow path when the temperature of
the refrigerant detected by the temperature detection unit rises,
and is switched to the second flow path when the temperature of the
refrigerant detected by the temperature detection unit falls.
6. The air conditioner according to claim 1, further comprising a
capillary, wherein the capillary is connected to the expansion
valve and the evaporator.
7. The air conditioner according to claim 1, wherein the
temperature detection unit is configured to detect the temperature
of the refrigerant in a state before the refrigerant is condensed
and liquefied in the condenser.
Description
TECHNICAL FIELD
[0001] The present invention relates to an air conditioner, and in
particular to an air conditioner in which the degree of opening of
an expansion valve is increased and decreased.
BACKGROUND ART
[0002] When an outdoor air temperature is high, required cooling
capability in cooling operation of an air conditioner increases,
and thus it is required to increase a flow rate of refrigerant
which circulates through the air conditioner. On the other hand,
when the outdoor air temperature is low, required cooling
capability in the cooling operation of the air conditioner
decreases, and thus it is required to decrease the flow rate of the
refrigerant which circulates through the air conditioner. That is,
in the cooling operation of the air conditioner, it is required to
appropriately adjust the flow rate of the refrigerant which
circulates through the air conditioner in accordance with the
outdoor air temperature.
[0003] Further, conventionally, air conditioners in which the
degree of opening of an expansion valve is adjustable have been
proposed. For example, Japanese Patent Laying-Open No. 56-151858
(PTD 1) discloses, as conventional art, a supercooling control
device for a refrigerator as an expansion valve whose degree of
opening is adjustable. In this supercooling control device for a
refrigerator, the temperature of refrigerant at an outlet of a
condenser is detected as thermal change by a temperature sensitive
cylinder attached to an outlet pipe. This thermal change is
converted into pressure change of a heated medium enclosed in the
temperature sensitive cylinder. A diaphragm is displaced by this
pressure change, and thereby a valve body connected to the
diaphragm is displaced. A gap between the valve body and a valve
seat is adjusted by the displacement of the valve body. Thereby, a
throttle amount of the valve is adjusted.
CITATION LIST
Patent Document
[0004] PTD 1: Japanese Patent Laying-Open No. 56-151858
SUMMARY OF INVENTION
Technical Problem
[0005] However, in the supercooling control device for a
refrigerator described in the above publication, the throttle
amount of the valve is adjusted to maintain a constant degree of
supercooling. Therefore, the throttle amount of the valve is
increased when the temperature of the refrigerant at the outlet of
the condenser is high, and the throttle amount of the valve is
decreased when the temperature of the refrigerant at the outlet of
the condenser is low. Since the outdoor air temperature is
proportional to a condensation temperature, in this supercooling
control device for a refrigerator, it is not possible to increase
the flow rate of the refrigerant when the outdoor air temperature
is high, and decrease the flow rate of the refrigerant when the
outdoor air temperature is low.
[0006] The present invention has been made in view of the
aforementioned problem, and an object of the present invention is
to provide an air conditioner capable of increasing an amount of
refrigerant which circulates through the air conditioner when an
outdoor air temperature is high, and decreasing the amount of the
refrigerant which circulates through the air conditioner when the
outdoor air temperature is low.
Solution to Problem
[0007] An air conditioner of the present invention includes a
compressor, a condenser, an expansion valve, an evaporator, and a
temperature detection unit. The compressor is configured to
compress refrigerant. The condenser is configured to condense the
refrigerant compressed by the compressor. The expansion valve is
configured to decompress the refrigerant condensed by the
condenser. The evaporator is configured to evaporate the
refrigerant decompressed by the expansion valve. The temperature
detection unit is attached to the condenser and is configured to
detect a temperature of the refrigerant in the condenser. The
expansion valve is configured to be capable of adjusting a flow
rate per unit time of the refrigerant flowing through the expansion
valve by adjusting a degree of opening of the expansion valve. The
degree of opening of the expansion valve is increased when the
temperature of the refrigerant detected by the temperature
detection unit rises, and the degree of opening of the expansion
valve is decreased when the temperature of the refrigerant detected
by the temperature detection unit falls.
Advantageous Effects of Invention
[0008] According to the air conditioner of the present invention,
the temperature detection unit detects the temperature of the
refrigerant in the condenser. Then, the degree of opening of the
expansion valve is increased when the temperature of the
refrigerant detected by the temperature detection unit rises, and
the degree of opening of the expansion valve is decreased when the
temperature of the refrigerant detected by the temperature
detection unit falls. The temperature of the refrigerant in the
condenser is proportional to an outdoor air temperature. Therefore,
the temperature of the refrigerant detected by the temperature
detection unit increases when the outdoor air temperature is high,
and the temperature of the refrigerant detected by the temperature
detection unit decreases when the outdoor air temperature is low.
Accordingly, the degree of opening of the expansion valve can be
increased when the outdoor air temperature is high, and the degree
of opening of the expansion valve can be decreased when the outdoor
air temperature is low. Thereby, an amount of the refrigerant which
circulates through the air conditioner can be increased when the
outdoor air temperature is high, and the flow rate of the
refrigerant which circulates through the air conditioner can be
decreased when the outdoor air temperature is low.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a view schematically showing a structure of a
refrigeration cycle of an air conditioner in a first embodiment of
the present invention.
[0010] FIG. 2 is a cross sectional view schematically showing a
structure of an expansion valve of the air conditioner in the first
embodiment of the present invention.
[0011] FIG. 3 is a cross sectional view for illustrating operation
of the expansion valve of the air conditioner in the first
embodiment of the present invention.
[0012] FIG. 4 is a view showing the relation between a cooling load
and an outdoor air temperature.
[0013] FIG. 5 is a view showing the relation between a required
refrigerant flow rate and the outdoor air temperature.
[0014] FIG. 6 is a view showing the relation between a required Cv
value and the outdoor air temperature.
[0015] FIG. 7 is a view showing the relation between a Cv value of
an expansion valve of an air conditioner in a second embodiment of
the present invention and the outdoor air temperature.
[0016] FIG. 8 is a cross sectional view schematically showing a
structure of the expansion valve of an air conditioner in the
second embodiment of the present invention.
[0017] FIG. 9 is an enlarged view showing a P portion in FIG. 8,
and is a cross sectional view for illustrating a first flow
path.
[0018] FIG. 10 is an enlarged view showing the P portion in FIG. 8,
and is a cross sectional view for illustrating a second flow
path.
[0019] FIG. 11 is a cross sectional view for illustrating a state
where refrigerant flows through a third hole of an expansion valve
in a variation of the second embodiment of the present
invention.
[0020] FIG. 12 is a cross sectional view for illustrating a state
where the refrigerant flows through the third hole and a fourth
hole of the expansion valve in the variation of the second
embodiment of the present invention.
[0021] FIG. 13 is a view schematically showing a structure of a
refrigeration cycle of an air conditioner in a third embodiment of
the present invention.
DESCRIPTION OF EMBODIMENTS
[0022] Hereinafter, embodiments of the present invention will be
described based on the drawings.
First Embodiment
[0023] FIG. 1 is a structural drawing of a refrigeration cycle of
an air conditioner in a first embodiment of the present invention.
First, referring to FIG. 1, a configuration of an air conditioner
10 in the first embodiment of the present invention will be
described. Air conditioner 10 of the present embodiment mainly has
a compressor 1, a condenser 2, an expansion valve 3, an evaporator
a condenser blower 5, an evaporator blower 6, a temperature
detection unit 7, a tube 8, and pipes PI1 to PI4. Compressor 1,
condenser 2, expansion valve 3, condenser blower 5, temperature
detection unit 7, and tube 8 are housed in an outdoor unit 11.
Evaporator 4 and evaporator blower 6 are housed in an indoor unit
12.
[0024] Compressor 1, condenser 2, expansion valve 3, and evaporator
4 communicate via pipes PI1 to PI4 and thereby constitute a
refrigeration cycle. Specifically, compressor 1 and condenser 2 are
connected with each other by pipe PI1. Condenser 2 and expansion
valve 3 are connected with each other by pipe PI2. Expansion valve
3 and evaporator 4 are connected with each other by pipe PI3.
Evaporator 4 and compressor 1 are connected with each other by pipe
PI4. The refrigeration cycle is configured such that refrigerant
circulates in order of compressor 1, pipe PI1, condenser 2, pipe
PI2, expansion valve 3, pipe PI3, evaporator 4, and pipe PI4. As
the refrigerant, for example, R410a, R32, R1234yf, or the like can
be used.
[0025] Compressor 1 is configured to compress the refrigerant.
Further, compressor 1 is configured to compress the sucked
refrigerant and discharge the compressed refrigerant. Compressor 1
is configured to have a variable capacity. Compressor 1 of the
present embodiment is configured such that its rotation number is
variably controllable. Specifically, the rotation number of
compressor 1 is adjusted by changing a drive frequency of
compressor 1 based on an instruction from a control device not
shown. Thereby, the capacity of compressor 1 is changed. This
capacity of compressor 1 is an amount of discharging the
refrigerant per unit time. That is, compressor 1 can perform high
capacity operation and low capacity operation. In the high capacity
operation, the operation is performed with a flow rate of the
refrigerant which circulates through a refrigerant circuit being
increased by increasing the drive frequency of compressor 1. In the
low capacity operation, the operation is performed with the flow
rate of the refrigerant which circulates through the refrigerant
circuit being decreased by decreasing the drive frequency of
compressor 1.
[0026] Condenser 2 is configured to condense the refrigerant
compressed by compressor 1. Condenser 2 is an air heat exchanger
including a pipe and a fin. Expansion valve 3 is configured to
decompress the refrigerant condensed by condenser 2. Expansion
valve 3 is configured to be capable of adjusting the flow rate of
the refrigerant flowing through expansion valve 3 by adjusting the
degree of opening of expansion valve 3. This flow rate of the
refrigerant flowing through expansion valve 3 is a flow rate per
unit time. Evaporator 4 is configured to evaporate the refrigerant
decompressed by expansion valve 3. Evaporator 4 is an air heat
exchanger including a pipe and a fin.
[0027] Condenser blower 5 is configured to adjust an amount of heat
exchange between outdoor air and the refrigerant in condenser 2.
Condenser blower 5 includes a fan 5a and a motor 5b. Motor 5b may
be configured to rotate fan 5a at a variable rotation number. Motor
5b may also be configured to rotate fan 5a at a constant rotation
number. Evaporator blower 6 is configured to adjust an amount of
heat exchange between indoor air and the refrigerant in evaporator
4. Evaporator blower 6 includes a fan 6a and a motor 6b. Motor 6b
may be configured to rotate fan 6a at a variable rotation number.
Motor 6b may also be configured to rotate fan 6a at a constant
rotation number.
[0028] Temperature detection unit 7 is attached to condenser 2.
Temperature detection unit 7 is configured to detect the
temperature of the refrigerant in condenser 2. Temperature
detection unit 7 is connected to expansion valve 3 via tube 8. The
degree of opening of expansion valve 3 is increased when the
temperature of the refrigerant detected by temperature detection
unit 7 rises, and the degree of opening of expansion valve 3 is
decreased when the temperature of the refrigerant detected by
temperature detection unit 7 falls. Temperature detection unit 7
detects the temperature of the refrigerant in a state before the
refrigerant is condensed and liquefied in condenser 2. Temperature
detection unit 7 is provided at a location in condenser 2 where it
can detect a condensation temperature of the refrigerant.
Accordingly, temperature detection unit 7 may be provided at an
inlet part of condenser 2, or at an intermediate part between an
inlet and an outlet of condenser 2.
[0029] Referring to FIGS. 1 and 2, configurations of specific
examples of expansion valve 3 and temperature detection unit 7 in
the present embodiment will be described in detail.
[0030] Expansion valve 3 is a temperature-type expansion valve.
Expansion valve 3 serving as a temperature-type expansion valve is
configured such that its degree of opening is adjusted in
accordance with a change in the temperature of the refrigerant in
condenser 2. Temperature detection unit 7 is a temperature
sensitive cylinder. In temperature detection unit 7 serving as a
temperature sensitive cylinder, refrigerant having the same
properties as those of the refrigerant used for a refrigerant cycle
is enclosed.
[0031] Expansion valve 3 has a case 31, a diaphragm 32, a valve
body 33, a valve seat 34, and a spring 35. Diaphragm 32 is attached
inside case 31 to partition the inside of case 31. Case 31 has a
first chamber S1 and a second chamber S2 partitioned by diaphragm
32.
[0032] Tube 8 is inserted into first chamber S1. First chamber S1
is configured such that the refrigerant enclosed in temperature
detection unit 7 serving as a temperature sensitive cylinder can
flow into and out of first chamber S1 via tube 8. That is, the
refrigerant enclosed in temperature detection unit 7 serving as a
temperature sensitive cylinder flows into and out of first chamber
S1 through tube 8, as indicated by a double-headed arrow A1 in FIG.
2.
[0033] Valve body 33, valve seat 34, and spring 35 are housed in
second chamber S2. Second chamber S2 has an inflow portion 31a and
an outflow portion 31b. Inflow portion 31a is connected to pipe
PI2. Outflow portion 31b is connected to pipe PI3. Second chamber
S2 is configured such that the refrigerant flowing through the
refrigeration cycle flows from pipe PI2 through inflow portion 31a
into second chamber S2, and flows out through outflow portion 31b
into pipe PI3. That is, as indicated by arrows A2 in FIG. 2, the
refrigerant flowing through the refrigeration cycle flows from
inflow portion 31a into second chamber S2, and flows out of outflow
portion 31b.
[0034] The pressure of first chamber S1 is equal to the pressure of
the refrigerant enclosed in temperature detection unit 7 serving as
a temperature sensitive cylinder. The pressure of second chamber S2
is equal to the pressure of the refrigerant flowing through the
refrigeration cycle. Diaphragm 32 is configured to be deformable by
a differential pressure between the pressure of first chamber S1
and the pressure of second chamber S2.
[0035] Valve body 33 has a first end E1, a second end E2, a shaft
portion 33a, and a tapered portion 33b. First end E1 is connected
to diaphragm 32. Second end E2 is connected to spring 35. Shaft
portion 33a and tapered portion 33b extend in an axial direction of
valve body 33. The axial direction of valve body 33 is a direction
in which first end E1 and second end E2 are opposed to each other,
as indicated by an arrow, A3 in FIG. 2.
[0036] Shaft portion 33a has first end E1. Tapered portion 33b has
second end E2. Shaft portion 33a is connected to tapered portion
33b on a side opposite to first end E1 in an axial direction A3.
Tapered portion 33b is configured such that its cross sectional
area continuously increases from shaft portion 33a toward second
end E2. Valve body 33 is configured to move in axial direction A3
due to deformation of diaphragm 32.
[0037] A gap is provided between tapered portion 33b of valve body
33 and valve seat 34. Expansion valve 3 is configured such that the
size of the gap between tapered portion 33b and valve seat 34 is
continuously changed by movement of valve body 33 in axial
direction A3 due to deformation of diaphragm 32. That is, expansion
valve 3 is configured such that a throttle amount of expansion
valve 3 changes in proportion to an amount of movement of valve
body 33 in axial direction A3.
[0038] Specifically, expansion valve 3 is configured such that the
gap between tapered portion 33b and valve seat 34 is decreased when
valve body 33 moves to a first end E1 side in axial direction A3.
That is, expansion valve 3 is configured such that the throttle
amount of expansion valve 3 is increased when valve body 33 moves
to the first end E1 side in axial direction A3. On the other hand,
expansion valve 3 is configured such that the gap between tapered
portion 33b and valve seat 34 is increased when valve body 33 moves
to a second end E2 side in axial direction A3. That is, expansion
valve 3 is configured such that the throttle amount of expansion
valve 3 is decreased when valve body 33 moves to the second end E2
side in axial direction A3.
[0039] Valve seat 34 is attached inside case 31. Valve seat 34 is
placed between inflow portion 31a and outflow portion 31b, in a
flow path extending from inflow portion 31a to outflow portion 31b.
Valve seat 34 is placed on the outside of tapered portion 33b of
valve body 33.
[0040] Spring 35 is connected to second end E2 of valve body 33 and
a bottom portion of case 31. Spring 35 is configured to bias valve
body 33 by an elastic force.
[0041] Next, a flow of the refrigerant in the refrigeration cycle
of air conditioner 10 of the present embodiment will be
described.
[0042] Referring to FIG. 1, the refrigerant flowing into compressor
1 is compressed by compressor 1, and becomes high-temperature
high-pressure gas refrigerant. The high-temperature high-pressure
gas refrigerant discharged from compressor 1 flows through pipe PI1
into condenser 2 serving as a radiator. The refrigerant flowing
into condenser 2 exchanges heat with the air in condenser 2.
Specifically, in condenser 2, the refrigerant is condensed by heat
radiation into the air, and the air is heated by the refrigerant.
High-pressure liquid refrigerant condensed by condenser 2 flows
through pipe PI2 into expansion valve 3.
[0043] The refrigerant flowing into expansion valve 3 is
decompressed by expansion valve 3, and becomes low-pressure
gas-liquid two-phase refrigerant. The refrigerant decompressed by
expansion valve 3 flows through pipe PI3 into evaporator 4. The
refrigerant flowing into evaporator 4 exchanges heat with the air
in evaporator 4. Specifically, in evaporator 4, the air is cooled
by the refrigerant, and the refrigerant becomes low-pressure gas
refrigerant. The refrigerant which is decompressed and becomes
low-pressure gas in evaporator 4 flows through pipe PI4 into
compressor 1. The refrigerant flowing into compressor 1 is
compressed again and pressurized, and then is discharged from
compressor 1.
[0044] Subsequently, referring to FIGS. 2 and 3, operations of the
specific examples of expansion valve 3 and temperature detection
unit 7 in the present embodiment will be described in detail.
[0045] Diaphragm 32 is deformed by the differential pressure
between a pressure A4 of first chamber S1 (an internal pressure of
temperature detection unit 7 serving as a temperature sensitive
cylinder) of case 31 and a pressure A5 of second chamber S2
(pressure of the refrigerant condensed by condenser 2).
[0046] When the temperature of the refrigerant enclosed in
temperature detection unit 7 serving as a temperature sensitive
cylinder increases, the pressure of first chamber S1 of case 31
becomes higher than the pressure of second chamber S2. When the
pressure of first chamber S1 of case 31 becomes higher than the
pressure of second chamber S2, diaphragm 32 is deformed to be
convex toward second chamber S2. Due to this deformation of
diaphragm 32, valve body 33 moves to the second end E2 side in
axial direction A3. Accordingly, the gap between tapered portion
33b and valve seat 34 is increased. That is, the throttle amount of
expansion valve 3 is decreased. Thereby, an amount of the
refrigerant flowing through expansion valve 3 is increased.
[0047] On the other hand, when the temperature of the refrigerant
enclosed in temperature detection unit 7 serving as a temperature
sensitive cylinder decreases, the pressure of first chamber S1 of
case 31 becomes lower than the pressure of second chamber S2. When
the pressure of first chamber S1 of case 31 becomes lower than the
pressure of second chamber S2, diaphragm 32 is deformed to be
convex toward first chamber S1. Due to this deformation of
diaphragm 32, valve body 33 moves to the first end E1 side in axial
direction A. Accordingly, the gap between tapered portion 33b and
valve seat 34 is decreased. That is, the throttle amount of
expansion valve 3 is increased. Thereby, the amount of the
refrigerant flowing through expansion valve 3 is decreased.
[0048] Further, the amount of movement of valve body 33 in axial
direction A3 is determined by the pressure of the refrigerant
enclosed in temperature detection unit 7 which flows into first
chamber S1, the pressure of the refrigerant in the refrigeration
cycle which flows into second chamber S2, and a bias force A6 of
spring 35 connected to valve body 33.
[0049] Next, the relation between an operation state of the
refrigeration cycle and the throttle amount wilt be described.
[0050] Cooling capability required for the refrigeration cycle is
determined by an outdoor air temperature. This is because, when the
outdoor air temperature increases, an indoor air temperature
increases in proportion to the increase of the outdoor air
temperature, and thereby more cooling capability is required.
Therefore, as shown in FIG. 4, the outdoor air temperature and the
cooling capability (cooling load=required capability) have a
proportional relation. Since the increase of the outdoor air
temperature and the increase of the condensation temperature have a
proportional relation, it can be considered that the axis of
abscissas of FIG. 4 also represents the condensation temperature.
This also applies to FIGS. 5 and 6.
[0051] Further, the cooling capability is proportional to a
refrigerant flow rate Gr of the refrigerant flowing into the
refrigeration cycle. This can also be explained from the fact that
cooling capability Qe is expressed by Qe=Gr.times..DELTA.he, using
a specific enthalpy difference .DELTA.he of the refrigerant at an
inlet and an outlet of the evaporator. Therefore, as shown in FIG.
5, the outdoor air temperature and a circulation flow rate
(required refrigerant flow rate) have a proportional relation.
[0052] Further, the throttle amount required for a temperature-type
expansion valve can be expressed by a flow rate coefficient (Cv
value). This Cv is expressed by the following equation (1), using
refrigerant circulation flow rate Gr, a condensation pressure P1,
an evaporation pressure P2, and a refrigerant density .rho.l at an
inlet of the expansion valve.
Cv = Gr 1 .rho. l ( P 1 - P 2 ) ( 1 ) ##EQU00001##
[0053] As expressed in equation (1), the refrigerant flow rate and
the Cv value have a proportional relation. Therefore, as shown in
FIG. 6, the refrigerant flow rate and the Cv value (required Cv
value) have a proportional relation.
[0054] In air conditioner 10 of the present embodiment, the flow
rate coefficient of expansion valve 3 is increased when the
temperature of the refrigerant detected by temperature detection
unit 7 rises, and the flow rate coefficient of expansion valve 3 is
decreased when the temperature of the refrigerant detected by
temperature detection unit 7 falls.
[0055] Next, the function and effect of the present embodiment will
be described.
[0056] According to air conditioner 10 of the present embodiment,
temperature detection unit 7 detects the temperature of the
refrigerant in condenser 2. Then, the degree of opening of
expansion valve 3 is increased when the temperature of the
refrigerant detected by temperature detection unit 7 rises, and the
degree of opening of expansion valve 3 is decreased when the
temperature of the refrigerant detected by temperature detection
unit 7 falls. The temperature of the refrigerant in condenser 2 is
proportional to the outdoor air temperature. Therefore, the
temperature of the refrigerant detected by temperature detection
unit 7 increases when the outdoor air temperature is high, and the
temperature of the refrigerant detected by temperature detection
unit 7 decreases when the outdoor air temperature is low.
Accordingly, the degree of opening of expansion valve 3 can be
increased when the outdoor air temperature is high, and the degree
of opening of expansion valve 3 can be decreased when the outdoor
air temperature is low. Thereby, the amount of the refrigerant
which circulates through air conditioner 10 can be increased when
the outdoor air temperature is high, and the flow rate of the
refrigerant which circulates through air conditioner 10 can be
decreased when the outdoor air temperature is low. Consequently,
the flow rate of the refrigerant which circulates through air
conditioner 10 can be adjusted appropriately in accordance with the
outdoor air temperature, in the cooling operation of air
conditioner 10.
[0057] Further, in air conditioner 10 of the present embodiment,
the throttle amount of expansion valve 3 can be changed in
accordance with the temperature of the refrigerant in condenser 2.
Accordingly, an increase in a discharge temperature at which the
refrigerant is discharged from compressor 1 can be suppressed, when
compared with a case where a capillary having a fixed throttle
amount is used as an expansion valve. Therefore, failure of
compressor 1 due to an increase in the discharge temperature at
which the refrigerant is discharged from compressor 1 can be
suppressed.
[0058] Further, in air conditioner 10 of the present embodiment,
the throttle amount of expansion valve 3 can be changed in
accordance with the temperature of the refrigerant in condenser 2.
Accordingly, the refrigerant at the outlet of evaporator 4 can be
controlled to be in a state close to the state of saturated gas, by
adjusting the degree of superheat, which is determined by a
difference between a temperature of the refrigerant at the outlet
of evaporator 4 and a temperature of the refrigerant inside
evaporator 4, to about 1K to 5K. Therefore, the refrigerant to be
sucked into compressor 1 can be controlled to be in the state close
to the state of saturated gas. Accordingly, performance of
compressor 1 can be improved, when compared with the case where a
capillary having a fixed throttle amount is used as an expansion
valve.
[0059] Further, in air conditioner 10 of the present embodiment,
the throttle amount of expansion valve 3 can be changed in
accordance with the temperature of the refrigerant in condenser 2.
Accordingly, the degree of supercooling at the outlet of condenser
2 can be secured. Therefore, noise caused by a gaseous phase
flowing into the inlet of expansion valve 3 can be reduced.
[0060] Further, in air conditioner 10 of the present embodiment,
the throttle amount of expansion valve 3 can be changed in
accordance with the temperature of the refrigerant in condenser 2.
Accordingly, high pressure of condenser 2 can be controlled.
Therefore, there is no need to make the rotation number of fan 5a
of condenser blower 5 variable in order to control the high
pressure of condenser 2. Consequently, a fixed blower in which the
rotation number of fan 5a is constant can be used as condenser
blower 5.
[0061] Further, in a case where refrigerant having a high discharge
temperature (for example, R410a, R32, R1234yf, or the like) is
used, when temperature detection unit 7 is attached at the outlet
of evaporator 4, it is not possible to decrease the temperature
under a condition where the discharge temperature increases, such
as an overload condition, in order to maintain a constant degree of
superheat. In contrast, in air conditioner 10 of the present
embodiment, since temperature detection unit 7 is attached to
condenser 2 and operation can be performed with the refrigerant to
be sucked into compressor 1 being in a gas-liquid two-phase state,
the discharge temperature can be decreased. As a result, failure of
compressor 1 can be prevented even in the case where the above
refrigerant having a high discharge temperature is used.
[0062] In air conditioner 10 of the present embodiment, expansion
valve 3 is a temperature-type expansion valve, and temperature
detection unit 7 is a temperature sensitive cylinder. Accordingly,
a temperature-type expansion valve can be used as expansion valve
3, and a temperature sensitive cylinder can be used as temperature
detection unit 7. Therefore, the size and the cost of air
conditioner 10 can be reduced, when compared with a case where an
electronic expansion valve is used. That is, in the case where an
electronic expansion valve is used, an electronic substrate for
driving the electronic expansion valve is required, and thus it is
necessary to secure a space for installing the electronic
substrate. Accordingly, the size of air conditioner 10 is
increased. In addition, since an actuator for driving the
electronic expansion valve and the like are required, the cost of
air conditioner 10 is increased. In contrast, in air conditioner 10
of the present embodiment, since a temperature-type expansion valve
can be used as expansion valve 3, and a temperature sensitive
cylinder can be used as temperature detection unit 7, the size and
the cost of air conditioner 10 can be reduced, when compared with
the case where an electronic expansion valve is used.
[0063] In air conditioner 10 of the present embodiment, the
rotation number of compressor 1 is variably controllable.
Accordingly, the cooling capability can be changed by variably
controlling the rotation number of compressor 1. Therefore, in a
state where the cooling capability is changed by variably
controlling the rotation number of compressor 1, the amount of the
refrigerant which circulates through air conditioner 10 can be
increased when the outdoor air temperature is high, and the flow
rate of the refrigerant which circulates through air conditioner 10
can be decreased when the outdoor air temperature is low.
[0064] In air conditioner 10 of the present embodiment, the flow
rate coefficient of expansion valve 3 is increased when the
temperature of the refrigerant detected by temperature detection
unit 7 rises, and the flow rate coefficient of expansion valve 3 is
decreased when the temperature of the refrigerant detected by
temperature detection unit 7 falls. Accordingly, expansion valve 3
can be adjusted in accordance with a change in flow rate
coefficient.
[0065] In air conditioner 10 of the present embodiment, temperature
detection unit 7 detects the temperature of the refrigerant in a
state before the refrigerant is condensed and liquefied in
condenser 2. Accordingly, the temperature of the refrigerant which
is proportional to the outdoor air temperature can be accurately
detected. Therefore, the flow rate of the refrigerant which
circulates through air conditioner 10 can be accurately adjusted in
accordance with the outdoor air temperature.
Second Embodiment
[0066] Hereinafter, components identical to those in the first
embodiment will be designated by the same reference numerals, and
the description thereof will not be repeated, unless otherwise
specified.
[0067] Referring to FIGS. 7 and 8, in a second embodiment of the
present invention, expansion valve 3 has a different configuration
when compared with that in the first embodiment described
above.
[0068] In the first embodiment, expansion valve 3 in which the
temperature of the refrigerant detected by temperature detection
unit 7 and the flow rate coefficient (Cv value) have linearity is
used. Expansion valve 3 of the second embodiment is configured such
that, when valve body 33 moves to a predetermined position, a flow
rate coefficient (Cv value) changes in a stepwise manner.
[0069] In expansion valve 3 of the present embodiment, valve body
33 has shaft portion 33a and a tubular portion 33c. Tubular portion
33c has a circumferential wall, an internal space surrounded by the
circumferential wall, and a first hole H1 and a second hole H2
provided in the circumferential wall. Second hole H2 has an opening
area smaller than that of first hole H1. First hole H1 and second
hole H2 communicate with the internal space. Valve seat 34 is
inserted into the internal space of tubular portion 33c from second
end E2. Valve seat 34 extends in axial direction A3. Expansion
valve 3 is configured such that the refrigerant flows from inflow
portion 31a, through one of first hole H1 and second hole H2, to
outflow portion 31b. Spring 35 has a first spring 35a and a second
spring 35b. First spring 35a and second spring 35b are connected to
second end E2 of valve body 33 and a bottom portion of valve seat
34.
[0070] Referring to FIGS. 8 to 10, expansion valve 3 has a first
flow path F1 and a second flow path F2. Referring to FIGS. 8 and 9,
first flow path F1 is a flow path extending from inflow portion
31a, through first hole H1, to outflow portion 31b. First flow path
F1 has a higher refrigerant flow rate and a higher flow rate
coefficient (Cv value). Referring to FIGS. 8 and 10, second flow
path F2 is a flow path extending from inflow portion 31a, through
second hole H2, to outflow portion 31b. Second flow path F2 has a
flow rate lower than that of first flow path F1. Second flow path
F2 has a lower refrigerant flow rate and a lower flow rate
coefficient (Cv value).
[0071] Referring to FIGS. 9 and 10, expansion valve 3 is switched
to first flow path F1 when the temperature of the refrigerant
detected by temperature detection unit 7 rises, and is switched to
second flow path F2 when the temperature of the refrigerant
detected by temperature detection unit 7 falls. Specifically, as
shown in FIG. 7, switching between first flow path F1 and second
flow path F2 is performed at a predetermined temperature A (for
example, an outdoor air temperature of 35.degree. C. based on the
ISO standard).
[0072] In air conditioner 10 of the present embodiment, expansion
valve 3 is switched to first flow path F1 when the temperature of
the refrigerant detected by temperature detection unit 7 rises, and
is switched to second flow path F2 when the temperature of the
refrigerant detected by temperature detection unit 7 falls.
Accordingly, switching between first flow path F1 and second flow
path F2 can be performed based on the temperature of the
refrigerant detected by temperature detection unit 7.
[0073] Further, in air conditioner 10 of the present embodiment,
since the flow rate coefficient (Cv value) can be increased in a
case where the outdoor air temperature or condensation temperature
reaches a temperature at which the discharge temperature may exceed
an upper limit temperature of compressor 1, for example, operation
can be performed with the refrigerant at an inlet of compressor 1
being in a gas-liquid two-phase state. Accordingly, the discharge
temperature is decreased, and thus operation can be safely
performed.
[0074] Further, in air conditioner 10 of the present embodiment,
since valve body 33 is processed easier than ordinary valve bodies,
the cost of expansion valve 3 can be reduced. Therefore, the cost
of air conditioner 10 can also be reduced.
[0075] Further, an ordinary air conditioner is provided with a
mechanism which can change the rotation number of a fan of a
condenser blower in order to control the condensation temperature.
For example, a DC fan is mounted. Generally, in a case where the
discharge temperature increases, operation of decreasing the
condensation temperature by increasing the rotation number of the
fan of the condenser blower is performed in order to protect a
compressor. In contrast, in the present embodiment, since operation
with an increased flow rate coefficient (Cv value) can be performed
in a case where the discharge temperature increases, the
refrigerant at the inlet of compressor 1 enters a gas-liquid
two-phase state, and the discharge temperature is decreased.
Accordingly, expansion valve 3 can compensate the operation of
protecting condenser blower 5. Consequently, air conditioner 10 of
the present embodiment is useful in a case where the rotation
number of fan 5a of condenser blower 5 is a constant speed.
[0076] Further, valve body 33 and valve seat 34 are not limited to
the above configurations, and they only have to be configured to
switch a flow path and change the flow rate coefficient (Cv value).
Referring to FIGS. 11 and 12, a variation of the present embodiment
will be described. In this variation, valve body 33 has a third
hole H3 and a fourth hole H4. Third hole H3 is provided in an upper
portion of valve body 33. Third hole H3 is configured such that the
refrigerant can always flow therethrough. In a case where the
refrigerant flows through only third hole H3, the refrigerant flow
rate is decreased, and the flow rate coefficient (Cv value) is
decreased. Fourth hole H4 is provided in a side portion of valve
body 33. Fourth hole H4 is configured such that the refrigerant
flows therethrough when valve body 33 moves down. In a case where
the refrigerant flows through fourth hole H4 in addition to third
hole H3, the refrigerant flow rate is increased, and the flow rate
coefficient (Cv value) is increased.
Third Embodiment
[0077] Referring to FIG. 13, air conditioner 10 of a third
embodiment of the present invention is different from air
conditioner 10 of the first embodiment described above in that the
former has a capillary 9.
[0078] Air conditioner 10 of the present embodiment further
includes capillary 9. Capillary 9 is connected to expansion valve 3
and evaporator 4. Accordingly, the refrigerant can be condensed by
capillary 9.
[0079] Since capillary 9 is placed after expansion valve 3, a
minimum throttle amount can be secured by capillary 9 even in a
case where expansion valve 3 has a failure. For example, in a case
where expansion valve 3 has a failure and a flow rate coefficient
(Cv value) is fixed at a high value although a required flow rate
coefficient (Cv value) is low, the refrigerant flows at a higher
flow rate, and thus the refrigerant enters a gas-liquid two-phase
state at the inlet of compressor 1. In the present embodiment,
since capillary 9 is provided after expansion valve 3, operation
can be performed in a state minimally throttled by capillary 9.
Consequently, safety of compressor 1 can be secured even in the
case where expansion valve 3 has a failure.
[0080] It should be understood that the embodiments disclosed
herein are illustrative and non-restrictive in every respect. The
scope of the present invention is defined by the scope of the
claims, rather than the description above, and is intended to
include any modifications within the scope and meaning equivalent
to the scope of the claims.
REFERENCE SIGNS LIST
[0081] 1: compressor; 2: condenser; 3: expansion valve; 4:
evaporator; 5: condenser blower; 6: evaporator blower; 7:
temperature detection unit; 8: tube; 9: capillary; 10: air
conditioner; 11: outdoor unit; 12: indoor unit; 31: case; 31a:
inflow portion; 31b: outflow portion; 32: diaphragm; 33: valve
body; 33a: shaft portion; 33b: tapered portion; 33c: tubular
portion; 34: valve seat; 35: spring; F1: first flow path; F2:
second flow path.
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